Conventionally, examples of systems which are researched as methods for purifying an exhaust gas include a so-called scrubber system which an exhaust gas collected in a tank is sprayed a chemical solution to perform gas treatment, and a system which photocatalyst apparatuses serving as exhaust gas treatment facilities are arranged on an exhaust gas flow path in series to purify an exhaust gas. The system utilizing the photocatalyst apparatuses mentioned above applies to reduce from 500 to 1000 ppm of toluene to about 170 ppm thereof which is included exhaust gas flowing through the flow path of an exhaust gas at 400 L/min.
In this case, the system, which uses larger number of photocatalyst apparatuses arranged in series, applies to reduce more of toluene. However, a problem exists in that the cost required for the purification is increased with the number of photocatalyst apparatuses which are not low-priced, and this is the conventional subject that should be resolved.